The present invention relates to plants or installations for producing a nonwoven web usually called by the generic name “spunbond”, which is formed from continuous synthetic filaments.
A plant or installation for producing a nonwoven web is already known that comprises, in succession from the top down, a means of generating a curtain of filaments, a slot attenuator for drawing the filaments of the curtain, a diffuser, that defines, for the attenuated filaments, a passage having a cross section, along the width of the curtain, that never decreases and, at least once, increases, and a conveyor for collecting the filaments exiting the diffuser.
The means for generating a curtain of filaments usually comprises an extruder intended to extrude a molten organic polymer through a spinneret drilled with numerous holes so as to form a curtain of filaments and, beneath the spinneret, a device for cooling the curtain of filaments. The slot attenuator for attenuating the filaments of the curtain generally has opposed side walls and opposed end walls that define an oblong inlet slot for receiving the filaments and an oblong outlet slot from which the filaments exit. A slot-shaped passage extends between the inlet and the outlet and the filaments pass therethrough, being attenuated by the injection of a stream of air into the slot-shaped passage, which stream is sufficient to attenuate the filaments. Beneath this slot attenuator for attenuating the filaments of the curtain is the diffuser, which is intended to spread out the incoming curtain. The web which thus forms on the collecting conveyor placed beneath the diffuser is thus more uniform.
The invention aims to further improve the uniformity of the web, this also being reflected in an improvement in the appearance and the mechanical strength.